Aqueous coating composition with soft touch upon drying

ABSTRACT

Aqueous coating compositions include dispersed polyurethane-vinyl polymer hybrid particles obtained by free-radical polymerization of at least one vinyl monomer in the presence of a polyurethane. The polyurethane and the vinyl polymer in the hybrid particles are present in a weight ratio of polyurethane to vinyl polymer ranging from 1:1 to 20:1, and the polyurethane is the reaction product of at least the following components: (a) from 5 to 40 wt. % of at least one organic difunctional isocyanate, (b) from 0.5 to 4 wt. % of an isocyanate-reactive compound containing ionic or potentially ionic water-dispersing groups having a molecular weight of from 100 to 500 g/mol, (c) from 40 to 80 wt. % of at least one diol having a molecular weight from 500 to 5000, (d) from 0 to 10 wt. % of at least one active-hydrogen chain extending compound with a functionality of at least 2 other than water, (e) from 0 to 10 wt. % of at least one diol having a molecular weight below 500 g/mol. The isocyanate and hydroxy groups on the components used are present in a respective mole ratio (NCO to OH) in the range of from 0.8:1 to 5:1.

This application is a continuation of commonly owned U.S. applicationSer. No. 16/542,229 filed Aug. 15, 2019 (now U.S. Pat. No. 10,883,015)which is a continuation of Ser. No. 15/538,054 filed Jun. 20, 2017 (nowU.S. Pat. No. 10,428,237), which is the U.S. national phase ofInternational Application No. PCT/EP2015/081040 filed Dec. 22, 2015,which designated the U.S. and claims priority to EP Patent ApplicationNo. 14200188.2, filed Dec. 23, 2014, the entire contents of each ofwhich are hereby incorporated by reference.

The present invention relates to an aqueous coating compositioncomprising a urethane-acrylic hybrid, a process for preparing such acomposition and a coating obtained from such a composition where thecoating provides a soft touch sensation with good transparency forsurfaces coated with this composition and/or where the coating has goodmechanical properties, like for example block resistance and/or goodbarrier properties like for example water and/or coffee resistance.

Coating compositions have long been used to produce coatings havingdesired coating characteristics. Traditionally, coatings have a visualfunction. For example, they protect the printed product and finish theprinting image. Haptic coatings provide additional properties. Hapticproperties also approach the other senses of a person and enable amulti-sensoric marketing. Feeling and touching is a subconscious processthat is regarded very important in the perception of materials. Coatinga surface with a soft-feel finish is intended to provide a soft, warmtouch sensation and also to give a sense of premium quality to theobject. Surfaces can be created that provide a soft or velvet feel orthat remind of suede. Luxurious and sophisticated are words often usedto describe the effect a haptic coating can produce.

Very often, the visual aspects of the substrates are important andtherefore the transparency of the coating is crucial. With a matt, buttransparent coating, the colours in printed materials can be enhancedsignificantly. For example, darker color palettes will appear moremuted, sophisticated, when a matt soft touch coating is applied. Alsowooden substrates maintain a natural impression by the use of thesecoatings.

A running behaviour as even as possible, a good scuff resistance and avery good block resistance are regarded as important properties in theapplication areas of these coatings. In case the coating has a poorblock resistance, there may be an undesirable adhesion between twocoated surfaces.

WO2010015494 describes a one-component coating composition based on ananionic polyurethane aqueous dispersion with a medium particle sizeabove 600 nm and a specified (low) acid content. Soft-touch propertiesare claimed, however it has been found that mechanical properties likeblock resistance and barrier properties like coffee resistance are poor.

The mechanical and barrier properties can be enhanced by use oftwo-component coating compositions as soft-touch coatings comprisingpolyisocyanate crosslinkers and aqueous binders as described inEP1647399, US2008021153, WO2012052406, US2010092766. However, thedisadvantages of such systems are the short pot life, handling of toxicpolyisocyanate crosslinkers and the side reaction of isocyanate withwater causing carbon dioxide bubbles trapped in the final coating.Furthermore, these two component systems may still demonstrate poortransparency.

One-component coating composition in the context of the presentinvention are understood as coating compositions which do not need to besubjected to crosslinking upon drying to obtain a coating. Thus theaqueous coating composition that is applied to a substrate does not needto contain a crosslinking component to obtain a coating, and thus thepot-life of one-component coating composition is longer than of coatingcomposition to which a crosslinking component needs to be added in orderto obtain a coating.

The object of the present invention is to provide aqueous coatingcompositions which can be applied as one-component coating compositionsand which may result in soft-touch coating combined with goodtransparency, good block resistance and/or good barrier properties likewater resistance, ethanol resistance, detergent resistance and/or coffeeresistance.

The inventors have surprisingly found that the use of urethane-acrylichybrids may result in improved mechanical properties like blockresistances and/or improved barrier properties like water resistance,ethanol resistance, detergent resistance and/or coffee resistance andalso combine good transparency in soft-touch coatings.

Accordingly, the object of the present invention has been achieved byproviding an aqueous coating composition having a soft-touch upon dryingcomprising dispersed polymer particles, wherein

-   -   (i) the dispersed polymer particles are polyurethane-vinyl        polymer hybrid particles obtained by free-radical polymerization        of at least one vinyl monomer in the presence of a polyurethane,    -   (ii) the polyurethane and the vinyl polymer in the hybrid        particles are present in a weight ratio of polyurethane to vinyl        polymer ranging from 1:1 to 20:1,    -   (iii) the polyurethane is the reaction product of at least the        following components:        -   (a) from 5 to 40 wt. % of at least one organic difunctional            isocyanate,        -   (b) from 0.5 to 4 wt. % of an isocyanate-reactive compound            containing ionic or potentially ionic water-dispersing            groups having a molecular weight of from 100 to 500 g/mol,        -   (c) from 40 to 80 wt. % of at least one diol having a            molecular weight from 500 to 5000 and preferably a glass            transition temperature from −110° C. to +110° C.,        -   (d) from 0 to 10 wt. % of at least one active-hydrogen chain            extending compound with a functionality of at least 2 (other            than water),        -   (e) from 0 to 10 wt. % of at least one diol having a            molecular weight below 500 g/mol,            where the amounts of (a), (b), (c), (d) and (e) are given            relative to the total amount of components used to prepare            the polyurethane from which the building blocks of the            polyurethane are emanated, and            where the isocyanate and hydroxy groups on the components            used to prepare the polyurethane are present in a respective            mole ratio (NCO to OH) in the range of from 0.8:1 to 5:1,            preferably from 1.05:1 to 5:1 and even more preferably from            1.1:1 to 3.5:1.

Preferably, the aqueous coating composition having a soft-touch upondrying comprises 90-99.9 wt. % dispersed polymer particles and 0.1-10wt. % of surfactant (whereby the amounts are given relative to the totalamount of dispersed polymer particles and surfactant).

More preferably, the aqueous coating composition comprises

-   (A) 75-99.7 wt. % of dispersed polymer particles,-   (B) 0.2 to 15 wt. % of rheology additive,-   (C) 0.1 to 10 wt. % of surfactant,    whereby the amounts of (A), (B) and (C) are given relative to the    total amount of dispersed polymer particles, rheology additive and    surfactant.

The aqueous coating composition according to the present inventioncomprises dispersed polyurethane-vinyl polymer hybrid particles obtainedby free-radical polymerization of at least one vinyl monomer in thepresence of a polyurethane, preferably an aqueous chain-extendedpolyurethane.

The polyurethane and the vinyl polymer in the hybrid particles arepresent in a weight ratio of polyurethane to vinyl polymer ranging from1:1 to 20:1, preferably from 2:1 to 16:1, even more preferably from 3:1to 12:1, even more preferably from 4:1 to 12:1 and even more preferablyfrom 4:1 to 10:1.

Methods for preparing polyurethanes are known in the art and aredescribed in for example the Polyurethane Handbook 2^(nd) Edition, aCarl Hanser publication, 1994, by G. Oertel. The polyurethane (A) may beprepared in a conventional manner by reacting at least one organicpolyisocyanate with at least one isocyanate-reactive component bymethods well known in the prior art. Isocyanate-reactive groups include—OH, —SH, —NH—, and —NH₂. Usually an isocyanate-terminated polyurethaneprepolymer is first formed which is then chain extended with an activehydrogen containing compound although a polyurethane may also beprepared without a chain extension step.

The polyurethane present in the aqueous coating composition of thepresent invention is obtained by reacting at least components (a), (b),(c) and optionally (d) and optionally (e).

Component (a)

Component (a) is at least one organic difunctional isocyanate. Theamount of component (a) relative to the total amount of components usedto prepare the polyurethane is from 5 to 40 wt. % and preferably from 10to 35 wt. %.

Examples of suitable organic difunctional isocyanates (component (a))include ethylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI),isophorone diisocyanate (IPDI), cyclohexane-1,4-diisocyanate,4,4′-dicyclohexylmethane diisocyanate (4,4′-H₁₂ MDI), p-xylylenediisocyanate, p-tetramethylxylene diisocyanate (p-TMXDI) (and its metaisomer m-TMXDI), 1,4-phenylene diisocyanate, hydrogenated 2,4-toluenediisocyanate, hydrogenated 2,6-toluene diisocyanate,4,4′-diphenylmethane diisocyanate (4,4′-MDI), polymethylene polyphenylpolyisocyanates, 2,4′-diphenylmethane diisocyanate,3(4)-isocyanatomethyl-1-methyl cyclohexyl isocyanate (IMCI) and1,5-naphthylene diisocyanate. Preferred organic difunctional isocyanatesare IPDI and/or H₁₂MDI which provide improved low yellowing. Mixtures oforganic difunctional isocyanates can be used. Conveniently component (a)comprises IPDI in an amount of at least 30 parts by weight, moreconveniently ≥50 parts by weight, most conveniently ≥70 parts by weight,relative to the total weight of component (a).

Component (b)

Component (b) is at least one isocyanate-reactive compound containingionic or potentially ionic water-dispersing groups and having a (numberaverage) molecular weight of from 100 to 500 g/mol. The amount ofcomponent (b) relative to the total amount of components used to preparethe polyurethane is from 0.5 to 4 wt. %, preferably from 0.8 to 3.2 wt.% and even more preferably from 1 to 2.5 wt %. As used herein,potentially anionic dispersing group means a group which under therelevant conditions can be converted into an anionic group by saltformation (i.e. deprotonating the group by a base).

Component (b) comprises any suitable polyol, preferably diol, containingionic or potentially ionic water-dispersing groups. Preferred ionicwater-dispersing groups are anionic water-dispersing groups. Preferredanionic water-dispersing groups are carboxylic, phosphoric and/orsulphonic acid groups. Examples of such compounds include carboxylcontaining diols, for example dihydroxy alkanoic acids such as2,2-dimethylol propionic acid (DMPA) or 2,2-dimethylolbutanoic acid(DMBA). Alternatively sulfonate groups may be used as potentiallyanionic water-dispersing groups. The anionic water-dispersing groups arepreferably fully or partially in the form of a salt. Conversion to thesalt form is optionally effected by neutralisation of the polyurethaneprepolymer with a base, preferably during the preparation of thepolyurethane prepolymer and/or during the preparation of the aqueouscomposition of the present invention. If the anionic water-dispersinggroups are neutralised, the base used to neutralise the groups ispreferably ammonia, an amine or an inorganic base. Suitable aminesinclude tertiary amines, for example triethylamine orN,N-dimethylethanolamine. Suitable inorganic bases include alkalihydroxides and carbonates, for example lithium hydroxide, sodiumhydroxide, or potassium hydroxide. A quaternary ammonium hydroxide, forexample N⁺(CH₃)₄(OH), can also be used. Generally a base is used whichgives counter ions that may be desired for the composition. For example,preferred counter ions include Li⁺, Na⁺, K⁺, NH₄ ⁺ and substitutedammonium salts. Cationic water dispersible groups can also be used, butare less preferred. Examples include pyridine groups, imidazole groupsand/or quaternary ammonium groups which may be neutralised orpermanently ionised (for example with dimethylsulphate). A very suitablecomponent (b) is dimethylol propionic acid (DMPA).

The neutralising agent is preferably used in such an amount that themolar ratio of the ionic and potentially ionic water dispersing groupsto the neutralizing groups of the neutralising agent are in the range offrom 0.7 to 5.0, more preferably from 0.8 to 3.0 and even morepreferably from 0.85 to 1.2.

Component (c)

Component (c) is at least one diol having a (number average) molecularweight from 500 to 5000 g/mol. As used herein, the number averagemolecular weight of a polyol is determined by multiplying the equivalentweight of the polyol with the OH functionality of the polyol (the OHfunctionality of the polyol is given by the supplier; in case the polyolis a diol, the OH functionality is 2). The equivalent weight of thepolyol is calculated by dividing 56100 by the OH number of the polyol.The OH number of the polyol is measured by titration a known mass ofpolyol according to ASTM D4274 and is expressed as mg KOH/g.

The amount of diol having a number average molecular weight from 500 to5000 g/mol (component (c)) relative to the total amount of componentsused to prepare the polyurethane is from 40 to 80 wt. %, preferably from45 to 75 wt. % and even more preferably from 50 to 70 wt. %. Such polyolmay be selected from any of the chemical classes of polyols that can beused in polyurethane synthesis. In particular the polyol may be apolyester polyol, a polyesteramide polyol, a polyether polyol, apolythioether polyol, a polycarbonate polyol, a polyacetal polyol, apolyvinyl polyol and/or a polysiloxane polyol.

The glass transition temperature T_(g) of the component (c) ispreferably from −110° C. to +110° C., more preferably from −100° C. to+40° C. and most preferably from −100° C. and −35° C. As used herein,the glass transition temperature is determined using differentialscanning calorimetry DSC according to the method as described in theinternational standard ISO 11357-2 (Plastics—Differential scanningcalorimetry (DSC)—Part 2: Determination of glass transition temperature)taking the midpoint temperature as T_(g) using a DSC Q1000 or Q2000 fromTA Instruments.

Preferred diols (c) are polyether diols that preferably comprisepolyalkyleneglycol (such as polypropyleneglycol (PPG);polyethyleneglycol (PEG); polytetrahydrofuran (also known as polyTHF,pTHF, polytetramethylene ether glycol (PTMEG)). Usefully PolyetherPolyol B is selected from the group consisting of PPG, PEG, pTHF andmixtures thereof, more usefully PPG and/or pTHF, most usefully pTHF andfor example those grades of pTHF available commercially (e.g. from BASF)under the trade designations pTHF650, pTHF1000 and/or pTHF2000

Component (d)

Component (d) is at least one active-hydrogen chain extending compoundwith a functionality of at least 2 (other than water). The amount ofcomponent (d) relative to the total amount of components used to preparethe polyurethane is from 0 to 10 wt. %. The amount of component (d)relative to the total amount of components used to prepare thepolyurethane is preferably from 0.5 to 10 wt. %, more preferably from 1to 7 wt. % and the isocyanate and hydroxy groups on the polyurethaneprecursors are then preferably present in a respective mole ratio (NCOto OH) in the range of from 1.05:1 to 5:1.

The aqueous composition may be prepared by dispersing anisocyanate-terminated polyurethane prepolymer in an aqueous medium andchain extending the prepolymer with at least one activehydrogen-containing chain extending compound with a functionality of atleast 2 in the aqueous phase. Active hydrogen-containing chain extenders(component (d)) which may be reacted with an isocyanate-terminatedpolyurethane prepolymer include amino-alcohols, primary or secondarydiamines or polyamines, hydrazine, and substituted hydrazines.

Examples of suitable active hydrogen-containing chain extenders withfunctionality 2 include alkylene diamines such as ethylene diamine andcyclic amines such as isophorone diamine. Also materials such ashydrazine, substituted hydrazines such as, for example, dimethylhydrazine, 1,6-hexamethylene-bis-hydrazine, carbodihydrazine, hydrazidesof dicarboxylic acids and sulphonic acids such as adipic acid mono- ordihydrazide, oxalic acid dihydrazide, isophthalic acid dihydrazide,hydrazides made by reacting lactones with hydrazide such asgammahydroxylbutyric hydrazide, bis-semi-carbazide, and bis-hydrazidecarbonic esters of glycols may be useful. Water itself may be effectiveas an indirect chain extender. Water-soluble active hydrogen chainextenders are preferred. Water itself may be used as an indirect chainextender because it will slowly convert some of the terminal isocyanategroups of the prepolymer to amino groups (via unstable carbamic acidgroups) and the modified prepolymer molecules will then undergo chainextension. However, this is very slow compared to chain extension usingthe active-hydrogen chain extenders.

Preferably the active-hydrogen chain extending compound withfunctionality 2 is selected from the group comprising, amino-alcohols,primary or secondary diamines, hydrazine, substituted hydrazines andsubstituted hydrazides.

Where the chain extender is other than water, for example, a hydrazine,it may be added to the aqueous dispersion of the isocyanate-terminatedpolyurethane prepolymer or, alternatively, it may already be present inthe aqueous medium when the isocyanate-terminated polyurethaneprepolymer is dispersed therein.

The chain extension may be conducted at convenient temperatures fromabout 5° C. to 95° C. or, more preferably, from about 10° C. to 60° C.

The total amount of active-hydrogen chain extending compound employed,if used, (apart from water) should be such that the ratio of activehydrogens in the chain extender to isocyanate groups in the polyurethaneprepolymer preferably is in the range from 0.1:1 to 2:1, more preferablyfrom 0.6:1 to 1.4:1 and especially preferred from 0.8 to 1.2.

Component (e)

Component (e) is at least one diol having a (number average) molecularweight below 500 g/mol, preferably in the range of 40 to 250 g/mol. Theamount of component (e) relative to the total amount of components usedto prepare the polyurethane is from 0 to 10 wt. % and preferably from0.1 to 10 wt. %. Examples include ethylene glycol, neopentylglycol,butane diol, pentane diol, hexane diol and 1,4 cyclohexanedimethanol.

The dispersed polyurethane-vinyl polymer hybrid particles present in theaqueous coating composition of the present invention is obtained byfree-radical polymerization of at least one vinyl monomer in thepresence of a polyurethane. At least 30 wt. %, more preferably at least50 wt. % and even more preferably at least 70 wt. % of the total amountof vinyl monomer(s) used to prepare the vinyl polymer is selected fromthe group consisting of methyl methacrylate, butyl acrylate, butylmethacrylate, acrylonitrile, styrene and mixtures of two or more of saidmonomers. Preferably, the vinyl monomer used to prepare the vinylpolymer is selected from the group consisting of methyl methacrylate,butyl acrylate, butyl methacrylate and mixtures thereof. More preferablyat least 30 wt. %, preferably at least 50 wt. % and more preferably atleast 70 wt. % of the total amount of vinyl monomer(s) used to preparethe vinyl polymer is methyl methacrylate.

The vinyl monomer(s) are polymerized using a conventional free radicalyielding initiator system. Suitable free radical yielding initiatorsinclude mixtures partitioning between the aqueous and organic phases.Suitable free-radical-yielding initiators include inorganic peroxidessuch as ammonium persulphate hydrogen peroxide, organic peroxides, suchas benzoyl peroxide, alkyl hydroperoxides such as t-butyl hydroperoxideand cumene hydroperoxide; dialkyl peroxides such as di-t-butyl peroxide;peroxy esters such as t-butyl perbenzoate and the like; mixtures mayalso be used. The peroxy compounds are in some cases advantageously usedin combination with suitable reducing agents (redox systems) such asiso-ascorbic acid. Azo compounds such as azobisisobutyronitrile may alsobe used. Metal compounds such as Fe. EDTA (EDTA is ethylene diaminetetracetic acid) may also be usefully employed as part of the redoxinitiator system. The amount of initiator or initiator system to use isconventional, e.g. within the range of 0.05 to 6 wt % based on theweight of vinyl monomer used.

The aqueous coating composition according to the present inventionpreferably comprises from 0.2 to 15 wt. % of rheology additive (relativeto the total amount of dispersed polymer particles, rheology additiveand surfactant), in particular associative thickener. Associativethickeners herein improve storage stability by increasing the viscosityof the composition. Examples of associative thickeners include watersoluble polymers, in particular hydrophobic modified water solublepolymers such as hydrophobically modified ethylene oxide urethane blockcopolymers (HEUR) which provides stabilisation and modifies the rheologyby acting as a thickener and hydrophobically modified alkali solubleemulsions (HASE). HEUR's tend to be mainly non-ionic and HASE's tend tobe anionic in nature. Preferably a hydrophobically modified ethyleneoxide urethane block copolymer is used with a sequence of at least 5ethylene oxide groups, preferably 10, most preferably 20.

The aqueous coating composition according to the present inventionpreferably comprises from 0.1 to 10 wt. % of surfactant (relative to thetotal amount of dispersed polymer particles, rheology additive andsurfactant), preferably 0.1 to 8% by weight, still more preferably 0.1to 5% by weight, especially 0.1 to 3% by weight, and most especially 0.3to 2.5% by weight. Surfactants and optionally high shear can be utilisedin any order to assist in the dispersion of isocyanate-terminatedpolyurethane prepolymer in water (even if it is self-dispersible).Suitable surfactants include but are not limited to conventionalanionic, cationic and/or nonionic surfactants such as Na, K and NH₄salts of dialkylsulphosuccinates, Na, K and NH₄ salts of sulphated oils,Na, K and NH₄ salts of alkyl sulphonic acids, Na, K and NH₄, alkylsulphates, alkali metal salts of sulphonic acids; fatty alcohols,ethoxylated fatty acids and/or fatty amines, and Na, K and NH₄ salts offatty acids such as Na stearate and Na oleate. Other anionic surfactantsinclude alkyl or (alk)aryl groups linked to sulphonic acid groups,sulphuric acid half ester groups (linked in turn to polyglycol ethergroups), phosphonic acid groups, phosphoric acid analogues andphosphates or carboxylic acid groups. Cationic surfactants include alkylor (alk)aryl groups linked to quaternary ammonium salt groups. Non-ionicsurfactants include polyglycol ether compounds and polyethylene oxidecompounds. Preferred surfactants are non-ionic surfactants.

In the present invention, the polyurethane of the polyurethane-vinylpolymer hybrid particles is preferably crosslinked. The crosslinkedpolyurethane is preferably prepared by further adding at least one ofthe following crosslinkers (f), (g) and (d′):

-   -   (f) at least one organic polyisocyanate with an average        functionality of >2.3, more preferred >2.5;    -   (g) at least one polyol having a molecular weight of 500-5000        g/mol and an average functionality of at least 2.3, more        preferably at least 2.6, most preferably at least 2.9, and        preferably a glass transition temperature from −110° C. and        +110° C.;    -   (d′) at least one active-hydrogen chain extending compound with        a functionality of 3 or higher in an amount of at least 50 wt. %        of component (d).        Component (f)

Preferably, the total amount of (f), (g) and (d′) are together more than3 wt. %, preferably more than 5 wt. %, and even more preferably morethan 10 wt. %, relative to the total amount of components used toprepare the polyurethane. Preferably, the total amount of (f), (g) and(d′) are together at most 20 wt. %, relative to the total amount ofcomponents used to prepare the polyurethane.

Component (f) is at least one organic polyisocyanate with an averagefunctionality of >2.3, more preferably >2.5. The amount of component (f)relative to the total amount of components used to prepare thepolyurethane is from 1 to 20 wt. %, more preferably from 5 to 15 wt. %,even more preferably from 8 to 12 wt. % (relative to the total amount ofcomponents used to prepare the polyurethane). Usefully the organicpolyisocyanate has an average NCO functionality of from 2.3 to 6.0, moreusefully from 2.5 to 4.0.

Component (f) is preferably selected from the group consisting ofhexamethylene diisocyanate isocyanurate such as for example DesmodurN3300 from Bayer, hexamethylene diisocyanate biuret such as for exampleDesmodur N3200 from Bayer, isophorone diisocyanate isocyanurate such asfor example Vestanat T1890 from Evonik and any mixture thereof.

Component (g)

Component (g) is at least one polyol having a (number average) molecularweight of 500-5000 g/mol and an average functionality of at least 2.3,more preferably at least 2.6, most preferably at least 2.9.

The amount of component (g) relative to the total amount of componentsused to prepare the polyurethane is from 1 to 10 wt. % and morepreferably from 2 to 7 wt. % of at least one polyol having a numberaverage molecular weight of 500-5000 g/mol (relative to the total amountof components used to prepare the polyurethane). Usefully the organicpolyol has an average OH functionality of from 2.3 to 4.5, more usefullyfrom 2.5 to 3.5.

The glass transition temperature T_(g) of the component (g) preferablyis from −110° C. to +110° C., more preferably from −100° C. to +40° C.and most preferably from −100° C. and −35° C. As used herein, the glasstransition temperature is determined using differential scanningcalorimetry DSC according to the method as described in theinternational standard ISO 11357-2 (Plastics—Differential scanningcalorimetry (DSC)—Part 2: Determination of glass transition temperature)taking the midpoint temperature as T_(g) using a DSC Q1000 or Q2000 fromTA Instruments.

In one embodiment of the present invention it is strongly preferred thatcomponent (g) comprises at least 80% (more preferably at least 90%, evenmore preferably at least 95%, most preferably at least 98%, for example100%) by weight of organic triol. The polyol may be a polyester polyol,a polyesteramide polyol, a polyether polyol, a polythioether polyol, apolycarbonate polyol, a polyacetal polyol, a polyvinyl polyol and/or apolysiloxane polyol. Component (g) is preferably selected from the groupconsisting of polyether polyols and/or polysiloxane polyol.

Component (d′)

Component (d′) is at least one active-hydrogen chain extending compoundwith a functionality of 3 or higher. The amount of component (d′) is atleast 50 wt. % of component (d). Thus, the amount of (d′) is included inthe amount of (d).

In one embodiment of the present invention it is strongly preferred thatcomponent (d′) comprises at least 80% (more preferably at least 90%,even more preferably at least 95%, most preferably at least 98%, forexample 100%) by weight of organic triamine. Component (d′) ispreferably selected from the group consisting of diethylene triamine,triethylene tetraamine, 4-amino-1,8-octanediamine of and any mixturethereof.

Preferably, the components from which the building blocks of thepolyurethane, present in the aqueous coating composition according tothe present invention, are emanated are components (a), (b), (c) andoptionally (d), (e), (f) and/or (g).

In a first stage of the preparation of the polyurethane present in theaqueous coating composition of the present invention, a polyurethaneprepolymer is obtained by reacting (a), (b), (c) and optionally (e)and/or (g) (where present) and the polyurethane prepolymer is obtainedprior to reacting components (d) and/or (f) (where present). Some or allof the vinyl monomers may be present at the commencement of thepreparation of the isocyanate-terminated prepolymer, or some or all ofthe vinyl monomers may be added during the course of the preparation, orsome or all of the vinyl monomers may be added after having prepared theisocyanate-terminated prepolymer or some or all of the vinyl monomersmay be added to the aqueous phase in which the urethane prepolymer isdispersed or some or all of the vinyl monomers may be added to theaqueous dispersion of the chain extended polyurethane (so after reactionwith component (d)) in which case the vinyl monomer(s) swell into thechain extended polyurethane particles). Preferably the vinyl monomersare not polymerised until after any optional chain extension has beencarried out.

In case crosslinker (d′) and/or (f) is used, the crosslinker is addedafter having finished the preparation of the isocyanate terminatedpolyurethane prepolymer obtained by reacting (a), (b), (c) andoptionally (e). When crosslinker (g) is used however, the compound istypically incorporated in the polyurethane prepolymer, together with(a), (b), (c) and optionally (e). The crosslinking reaction ispreferably effected during the chain-extension of the polyurethaneprepolymer, which chain extension is preferably effected in thepolyurethane prepolymer aqueous dispersion. In case a component (f) isused as crosslinker, such crosslinker may be added to the isocyanateterminated prepolymer prior to dispersing of to the isocyanateterminated prepolymer. In case a component (d′) is used as crosslinker,such crosslinker is added after having dispersed the isocyanateterminated polyurethane prepolymer and/or is added to the water in whichthe isocyanate terminated polyurethane prepolymer is dispersed. In casecomponent (g) is used as crosslinker, component (g) will preferably beincorporated in the polyurethane prepolymer resulting in some branchingof the polyurethane prepolymer, but the crosslinking into a network willbe effected during the chain extension step.

In a special embodiment the coating composition further comprises a slipadditive. Examples are but not limited to polysiloxanes andfluorocomponents to adjust the desired feel.

Preferably, the aqueous coating composition of the present invention isa one-component composition.

The aqueous coating composition and/or coatings of the invention containorganic solvent in an amount of preferably at most 20000 ppm, morepreferably at most 10000 ppm, more preferably at most 5000 ppm, morepreferably at most 3000 ppm, even more preferably at most 1000 ppm, evenmore preferably at most 500 ppm. The aqueous coating composition and/orcoatings of the invention are more preferably free of organic solvent.

The mean particle size (D[0.5]) of the dispersed polymer particles (A)is preferably greater than 0.5 micron, more preferably greater than 0.8micron, most preferably greater than 1.2 micron and especially preferredgreater than 1.5 micron. D[0.5] means that the first 50 volume % of theparticle size distribution has a mean particle size X.

The mean particle size (D[0.9]) of the dispersed polymer particles (A)is preferably less than 20 micron, more preferably less than 15 micron,more preferably less than 10 micron and especially preferred less than 6micron. D[0.9] means that the first 90 volume % of the particle sizedistribution has a mean particle size Y. In the context of the presentinvention, the particle size and particle size distribution are measuredby laser diffraction using a Mastersizer 3000 from Malvern.

Gloss measurements are made with 60° or 85° geometry of angles andapertures. Preferably the 60° gloss of the aqueous coating compositionafter drying is ≤10. Preferably the 85° gloss of the aqueous coatingcomposition after drying is ≤60.

Preferably, the delta L value of the aqueous coating composition afterdrying on a black substrate is ≤30, more preferably ≤25 and even morepreferably 20.

The present invention further relates to a process for preparing anaqueous coating composition according to any one of the preceding claimscomprising the following steps:

-   -   a) reaction of components (a) to (c) to form a polyurethane;    -   b) optionally neutralising the polyurethane;    -   c) forming an aqueous dispersion of the polyurethane in water;    -   d) optionally adding active-hydrogen chain extending compound        (d)    -   e) optionally adding at least one crosslinker (f), (g) and/or        (d′);    -   f) adding at least a surfactant;    -   g) adding at least rheology additive;    -   h) adding vinyl monomer;    -   i) adding a radical initiator.        where steps b), c), e), f), g), h) and i) may be in any order.

There is further provided according to the present invention a coatingobtained by (i) applying an aqueous coating composition according to anyone of claims 1 to 24 to a substrate and (ii) drying the aqueous coatingcomposition by evaporation of volatiles to obtain a coating, wherein thecoating has a soft touch and whereby no additional chemical crosslinkingreaction is needed after having applied the coating composition on thesubstrate like for example UV curing and/or curing with the aid of acrosslinker. The aqueous coating composition according to the presentinvention allows to obtain a coating solely by drying the aqueouscoating composition by evaporation of volatiles; a crosslinker and/orexternal curing trigger such as UV-radiation is not needed.

The coating composition of this invention can be used either to protecta substrate underneath, or to improve the aesthetics and hapticperception of a subject, or to provide additional properties to thesubject or a combination of these. This coating composition can beapplied to various substrates, such as wood, metal, paper, plastic,plastic films. The coating can be applied in various ways, such asspraying, brushing, roll-to-roll, curtain coating, printing (flexo,gravure). The coating compositions according to the invention canadvantageously be used in packaging (such as laminating plastic films,paper and board), in printing applications such as overprint varnishes,for wood furniture, for parquet flooring, for flexible flooring (such asPVC, linoleum), for decorative paints. Preferably, the substrate is apaper substrate, a plastic substrate or a wooden substrate (or acombination thereof).

The present invention further relates to the use of the aqueous coatingcomposition according to the present invention to obtain a coatinghaving a soft touch.

The present invention is now illustrated by reference to the followingexample. Unless otherwise specified, all parts, percentages and ratiosare on a weight basis.

Materials & abbreviations used:

-   PPG2000=polypropyleneglycol with a number average molecular weight    of 2000 g/mol=component (c)-   pTHF1000=polytetrahydrofuran with a number average molecular weight    of 1000 g/mol=component (c)-   DMPA=dimethylol propionic acid=component (b)-   IPDI=isophorone diisocyanate=component (a)-   MMA=methylmethacrylate=vinyl monomer-   Styrene=vinyl monomer-   TEA=triethylamine=neutralizer-   DETA=diethylene triamine=component (d′)-   Desmodur N3300 from Bayer=Hexamethylene diisocyanate    isocyanurate=component (f)-   Vestamin A95 from Evonik=a 50% solution of    2-[(2-aminoethyl)amino]ethanesulfonic acid, sodium salt in    water=component (d)-   SA=stoechiometric amounts-   Tegofoamex 805=Defoamer ex Tego-   Nopco DSX 1514=Associative thickener ex BASF-   Disponil AFX3070=Surfactant ex BASF

EXAMPLES AND COMPARATIVE EXPERIMENTS

The following examples and comparative experiments were prepared andcoatings were obtained and tested. The compositions of the examples isshown in Table 4 and results are as shown in Tables 1-3.

Staining Resistances

The aqueous coating composition is applied to a test chart from Lenetaat a wet layer thickness of 50 micron and dried at room temperature forone hour and subsequently for 16 hours at 50° C.

Cotton wool, soaked with various testing liquids (water, 50% ethanol inwater, coffee and “Cif” a commonly used Dutch detergent) were placed onthe coatings and covered to prevent fast evaporation. The cotton woolwas removed after 16 hours at room temperature. The water and detergentresistances were assessed directly and the ethanol resistance wasassessed after one hour. Poor=severely impaired, moderate=impaired,good=minor impairment, very good=hardly impaired, excellent=noimpairment

Anti-Blocking

The aqueous coating composition is applied to a test chart from Lenetaat a wet layer thickness of 50 micron and dried at room temperature forone hour and subsequently for 16 hours at 50° C. The coated surface iscut into pieces of 50×150 mm and folded so that both lacquer againstlacquer and lacquer against backside is tested. The folded substrate isput a so-called block tester and the pressure is set at 1 kg/m2 or 6kg/m2. The block tester is put in an oven at 52° C. for 16 hours. Afterthis treatment, the test specimen is taken out of the block tester andconditioned at room temperature for one hour. The blocking is determinedby pulling the two test specimen apart by hand. The degree of blockingis determined on the basis of the easiness of pulling the two testspecimens apart. It is also very important that the coating is notimpaired or damaged. Poor=severely impaired, moderate=impaired,good=minor impairment, very good=hardly impaired, excellent=noimpairment.

Gloss Measurements

BYK Gardner micro-TRI-gloss 20-60-85 glossmeter in accordance with ASTMD523-89.

Particle Size Measurements

A Mastersizer 3000 from Malvern, which measures the particle size andparticle size distribution by laser diffraction, was used to measure theparticle size the dispersed polymer particles (A).

The technique of laser diffraction is based on the principle thatparticles passing through a laser beam will scatter light at an anglethat is directly related to their size. The observed scatteringintensity is also dependent on particle sizes. Large particles scatterlight at narrow angles with high intensity, whereas small particlesscatter light at wider angles but with low intensity.

Comparative Example A

Comparative example A is a polyurethane dispersion that isprecrosslinked by the use of a triisocyanate. However, it is nourethane/vinyl hybrid dispersion.

A 2000 cm3 flask equipped with a thermometer and overhead stirrer wascharged with 873.8 g of PPG2000 (OH-value=55 mg KOH/g), 22.2 g DMPA and264.0 g IPDI. This mixture was heated to 50° C. and Zinc neodecanoate(0.49 g) was added. The reaction was allowed to exotherm to 95° C. Afterthe exotherm was complete the reaction was kept at 95° C. for 2 hours.Subsequently, the prepolymer is cooled to 75° C. and 139.5 g of DesmodurN3300 is added. The isocyanate content of the prepolymer was 5.89%(theoretical 6.17%). 20.1 g of triethylamine was added to the prepolymerto neutralise the acid groups and the mixture was homogenised withstirring.

A 3000 cm3 dispersion vessel with a thermometer and overhead stirrer wascharged with 1677.3 g of demineralised water, 9.2 g of Tegofoamex 805(obtained from Tego), 62.8 of DSX 1514 (obtained from BASF) and 19.8 gDisponil AFX3070 (obtained from BASF). The mixture was homogenised withstirring and the temperature was adjusted to 20-22° C.

817.6 g of the neutralised prepolymer was dispersed in the aqueous phaseadjusting the stir rate to improve dispersing of the prepolymer ifnecessary, while maintaining the temperature of the aqueous phase below27° C. After the give amount of prepolymer was dispersed, stirring wascontinued for 5 minutes after which 98.12 g of a 16.4% hydrazinesolution was added to provide the chain extended polyurethanedispersion.

The resulting polyurethane dispersion had a solids content of 31.8 wt %,a pH of 7.3 and a viscosity of 966 cps. The dispersion has a D(0.5) meanparticle size of 2.0 micron and a D(0.9) mean particle size of 4.3micron

Comparative Example B

Comparative Example B is a polyurethane dispersion, which is used as anexample in patent WO 2010/015494. Soft feel properties are good, butresistance profile is very poor.

A 2000 cm3 flask equipped with a thermometer and overhead stirrer wascharged with 790.2 g of pTHF1000 (OH-value=112 mg KOH/g), 30.0 g DMPAand 0.44 g phosphoric acid 85%. A nitrogen atmosphere was applied. Themixture was homogenised at 40° C. for 10 minutes, before 429.3 g IPDIwas added. This mixture was heated to 60° C. and kept at thistemperature for 60 minutes. Subsequently reaction was carried out at 80°C. until the NCO-content of the mixture was 5.96%, the prepolymer wascooled down to 75° C. and 22.7 g of triethylamine was added to theprepolymer.

A 2000 cm3 dispersion vessel with a thermometer and overhead stirrer wascharged with 777.4 g of demineralised water and 375.6 g of theneutralised prepolymer was dispersed in the aqueous phase whilemaintaining the temperature of the aqueous phase below 35° C. After thegive amount of prepolymer was dispersed, stirring was continued for 5minutes after which a mixture of 43.2 g of a 15.7% hydrazine solutionand 37.3 g of Vestamin A95 was added to provide the chain extendedpolyurethane dispersion.

The resulting polyurethane dispersion had a solids content of 32.6 wt %,a pH of 9.2 and a viscosity of 10 cps. The dispersion has a D(0.5) meanparticle size of 2.6 micron and a D(0.9) mean particle size of 7.6micron.

Comparative Example C

Comparative example C is a urethane/vinyl dispersion with a DMPA-contentabove the limits specified in claim 1. This results in the formation ofsmall particles. The final coating has a high gloss and no soft feelproperties.

A 2000 cm3 flask equipped with a thermometer and overhead stirrer wascharged with 742.6 g of pTHF1000 (OH-value=112 mg KOH/g), 60.0 g DMPA,300.0 g MMA, 0.3 g of 2,6-di-tert-butyl-p-cresol and 397.4 g IPDI. Thismixture was heated to 70° C. and the reaction was allowed to exotherm to95° C. After the exotherm was complete the reaction was kept at 95° C.for 2 hours. Subsequently, the prepolymer is cooled to 75° C. and theisocyanate content of the prepolymer was determined: 3.26% (theoretical3.34%). 40.7 g of triethylamine (0.9 SA) was added to the prepolymer toneutralise the acid groups and the mixture was homogenised withstirring.

A 2000 cm3 dispersion vessel with a thermometer and overhead stirrer wascharged with 1075.0 g of demineralised water. 616.3 g of the neutralisedprepolymer was dispersed in the aqueous phase adjusting the stir rate toimprove dispersing of the prepolymer if necessary, while maintaining thetemperature of the aqueous phase below 27° C. After the give amount ofprepolymer was dispersed, stirring was continued for 5 minutes afterwhich 43.2 g of a 16.4% hydrazine solution was added to provide thechain extended polyurethane dispersion.

The radical polymerization was initiated by the addition of 0.30 g oftertiary butyl hydroperoxide, 0.006 g of iron(II)EDTA and a subsequentaddition of 36.4 g of a 1.0% solution of isoascorbic acid indemineralized water.

The resulting urethane/acrylic hybrid dispersion with a urethane/acrylicratio of 80/20 had a solids content of 33.3 wt %, a pH of 8.0 and aviscosity of 181 cps. The dispersion has a D(0.9) mean particle size of45 nm (0.045 micron).

Example 1

Example 1 is the 80/20 urethane/vinyl modification of ComparativeExample A. The hybrid is formed by swelling the polyurethane particleswith methylmethacrylate and subsequent polymerisation.

A 1000 cm3 flask equipped with a thermometer and overhead stirrer wascharged with 301.5 g of dispersion A. 33.9 g of demineralized water wasadded and the temperature was increased to 30° C. 24.1 g of MMA wasdosed to the reactor and the mixture was stirred gently for 60 minutes.

The radical polymerization was initiated by the addition of 0.19 g oftertiary butyl hydroperoxide, 0.009 g of iron(II)EDTA and a subsequentaddition of 13.3 g of a 1.36% solution of isoascorbic acid indemineralized water.

The resulting urethane/acrylic hybrid dispersion with a urethane/acrylicratio of 80/20 had a solids content of 31.3 wt %, a pH of 8.4 and aviscosity of 4690 cps. The dispersion has a D(0.5) mean particle size of2.0 and a D(0.9) mean particle size of 4.3 micron

Example 2

Example 2 is the 90/10 urethane/vinyl hybrid modification of ComparativeExample A. The hybrid is formed by dispersion of the polyurethaneprepolymer into an aqueous phase that contains styrene. After chainextension of the polyurethane, the vinyl monomers are polymerised insidethe urethane particles.

A 1000 cm3 flask equipped with a thermometer and overhead stirrer wascharged with 268.9 g of PPG2000 (OH-value=55 mg KOH/g), 6.82 g DMPA and81.2 g IPDI. This mixture was heated to 50° C. and Zinc neodecanoate(0.15 g) was added. The reaction was allowed to exotherm to 95° C. Afterthe exotherm was complete the reaction was kept at 95° C. for 2 hours.Subsequently, the prepolymer is cooled to 75° C. and 42.9 g of DesmodurN3300 is added. The isocyanate content of the prepolymer was 5.68%(theoretical 6.17%). 6.18 g of triethylamine was added to the prepolymerto neutralise the acid groups and the mixture was homogenised withstirring.

A 2000 cm3 dispersion vessel with a thermometer and overhead stirrer wascharged with 680.7 g of demineralised water, 3.4 g of Tegofoamex 805(obtained from Tego), 23.2 g DSX 1514 (obtained from BASF), 7.3 gDisponil AFX3070 (obtained from BASF) and 33.0 g of styrene. The mixturewas homogenised with stirring and the temperature was adjusted to 20-22°C.

301.6 g of the neutralised prepolymer was dispersed in the aqueous phaseadjusting the stir rate to improve dispersing of the prepolymer ifnecessary, while maintaining the temperature of the aqueous phase below27° C. After the give amount of prepolymer was dispersed, stirring wascontinued for 5 minutes after which 36.2 g of a 16.4% hydrazine solutionwas slowly added to provide the chain extended polyurethane dispersion.

After 15 minutes of mixing, the radical polymerization was initiated bythe addition of 0.12 g of tertiary butyl hydroperoxide, 0.006 g ofiron(II)EDTA and a subsequent addition of 8.20 g of a 1.34% solution ofisoascorbic acid in demineralized water.

The resulting urethane/acrylic hybrid dispersion with a urethane/acrylicratio of 90/10 had a solids content of 29.2 wt %, a pH of 7.3 and aviscosity of 1360 cps. The dispersion has a D(0.5) mean particle size of2.4 micron and a D(0.9) mean particle size of 5.1 micron.

TABLE 1 EtOH Anti- Water resistance Gloss Soft blocking resistance(after Detergent Example 60° feel (L/L) (direct) recovery) (direct) CompA 11 Very Poor Poor Poor Moderate good Comp B 0.4 Very Poor Poor PoorPoor good Comp C 79 None Not Not Not Not measured measured measuredmeasured Ex1 2.4 Very Very Good Excellent Moderate good good Ex 2 2.4Very Good Good Good Very good good

The coating compositions of Comparative example A and B result incoatings with low gloss values and soft feel coatings. However, thecoating properties like anti-blocking and staining resistances (barrierproperties) are inferior. The properties of comparative example A aresignificantly improved by the polymerisation of vinyl monomers insidethe polyurethane particles, as shown in Examples 1 and 2. These hybridparticles, in which different polymers are intimately mixed, provideanti-blocking properties, as well as higher resistance levels.

Comparative example C shows that a “regular” small particle sizepolyurethane dispersion does not provide the desired low gloss and softfeel properties. Hence the barrier properties and stain resistance arenot determined.

Example 3

Example 3 shows that the anti-blocking properties can be improvedsignificantly by modifying comparative example B into a urethane/vinylhybrid. Also the resistance profile is improved.

A 1000 cm3 flask equipped with a thermometer and overhead stirrer wascharged with 275.0 g of the dispersion from comparative example B, 48.2g of water and 33.5 g of MMA. After 60 minutes of mixing, the radicalpolymerization was initiated by the addition of 0.18 g of tertiary butylhydroperoxide, 0.008 g of iron(II)EDTA and a subsequent addition of 9.30g of a 1.82% solution of isoascorbic acid in demineralized water.

The resulting urethane/acrylic hybrid dispersion with a urethane/acrylicratio of 70/30 had a solids content of 27.6 wt %, a pH of 9.1 and aviscosity of 20 cps. The dispersion has a D(0.5) mean particle size of2.4 micron and a D(0.9) mean particle size of 7.5 micron.

Example 4

Example 4 shows that the anti-blocking properties and chemicalresistances can be improved significantly by modifying comparativeexample B into a precrosslinked urethane/vinyl hybrid according to ourinvention.

A 1000 cm3 flask equipped with a thermometer and overhead stirrer wascharged with 328.0 g of pTHF1000 (OH-value=112 mg KOH/g), 12.5 g DMPAand 0.18 g phosphoric acid 85%. A nitrogen atmosphere was applied. Themixture was homogenised at 40° C. for 10 minutes, before 178.2 g IPDIwas added. This mixture was heated to 60° C. and kept at thistemperature for 60 minutes. Subsequently reaction was carried out at 80°C. for 120 minutes. After the prepolymer is cooled to 75° C. and 31.2 gof Desmodur N3300 is added, the NCO-content of the mixture was 7.02%.Subsequently, 9.4 g of triethylamine was added to the prepolymer.

A 2000 cm3 dispersion vessel with a thermometer and overhead stirrer wascharged with 953.6 g of demineralised water and 13.75 g Disponil AFX3070(obtained from BASF) and 476.2 g of the neutralised prepolymer wasdispersed in the aqueous phase while maintaining the temperature of theaqueous phase below 35° C. After the give amount of prepolymer wasdispersed, stirring was continued for 5 minutes after which a mixture of66.5 g of a 15.7% hydrazine solution was added to provide the chainextended polyurethane dispersion.

A 1000 cm3 flask equipped with a thermometer and overhead stirrer wascharged with the polyurethane dispersion from this example, 24.0 g ofwater and 19.2 g of MMA. After 60 minutes of mixing, the radicalpolymerization was initiated by the addition of 0.20 g of tertiary butylhydroperoxide, 0.007 g of iron(II)EDTA and a subsequent addition of10.66 g of a 1.36% solution of isoascorbic acid in demineralized water.

The resulting urethane/acrylic hybrid dispersion with a urethane/acrylicratio of 80/20 had a solids content of 31.9 wt %, a pH of 8.1 and aviscosity of 26 cps. The dispersion has a D(0.5) mean particle size of2.3 micron and a D(0.9) mean particle size of 4.9 micron

TABLE 2 EtOH Anti- Water resis- Deter- block- resis- tance Coffee gentGloss Soft ing tance (after resis- resis- 60° feel L/L) (direct)recovery) tance tance Comp B 11 Very Good Poor Poor Poor Poor good Ex 32.4 Very Very Good Poor Good Very good good good Ex 4 0.4 Good Very Goodmoderate Good Very good good

Comparative Example D

Comparative example D is a polyurethane dispersion that isprecrosslinked by the use of a triisocyanate. However, it is nourethane/vinyl hybrid dispersion.

A 2000 cm3 flask equipped with a thermometer and overhead stirrer wascharged with 1072.2 g of pTHF1000 (OH-value=112 mg KOH/g), 32.2 g DMPAand 581.9 g IPDI. This mixture was heated to 50° C. and Zincneodecanoate (0.31 g) was added. The reaction was allowed to exotherm to95° C. After the exotherm was complete the reaction was kept at 95° C.for 2 hours. Subsequently, the prepolymer is cooled to 75° C. and 202.8g of Desmodur N3300 is added. The isocyanate content of the prepolymerwas 8.02% (theoretical 8.16%). 29.2 g of triethylamine was added to theprepolymer to neutralise the acid groups and the mixture was homogenisedwith stirring.

A 2000 cm3 dispersion vessel with a thermometer and overhead stirrer wascharged with 972.7 g of demineralised water, 4.7 g of Tegofoamex 805(obtained from Tego), 36.9 g of DSX 1514 (obtained from BASF) and 15.3 gDisponil AFX3070 (obtained from BASF). The mixture was homogenised withstirring and the temperature was adjusted to 20-22° C.

421.9 g of the neutralised prepolymer was dispersed in the aqueous phaseadjusting the stir rate to improve dispersing of the prepolymer ifnecessary, while maintaining the temperature of the aqueous phase below27° C. After the give amount of prepolymer was dispersed, stirring wascontinued for 5 minutes after which a mixture of 26.3 g DETA and 26.3 gof water was added to provide the chain extended polyurethanedispersion.

The resulting polyurethane dispersion had a solids content of 31.2 wt %,a pH of 8.4 and a viscosity of 1420 cps. The dispersion has a D(0.5)mean particle size of 1.8 micron and a D(0.9) mean particle size of 5.0micron.

Example 5

Example 5 is the 90/10 urethane/vinyl modification of ComparativeExample D. The hybrid is formed by the presence of methyl methacrylateduring the dispersion process of the polyurethane. In this way, thevinyl monomers are migrating into the polyurethane particles and afterchain extension reaction of the polyurethane, the monomers arepolymerised inside the particles.

A 2000 cm3 flask equipped with a thermometer and overhead stirrer wascharged with 1072.2 g of pTHF1000 (OH-value=112 mg KOH/g), 32.2 g DMPAand 581.9 g IPDI. This mixture was heated to 50° C. and Zincneodecanoate (0.31 g) was added. The reaction was allowed to exotherm to95° C. After the exotherm was complete the reaction was kept at 95° C.for 2 hours. Subsequently, the prepolymer is cooled to 75° C. and 202.8g of Desmodur N3300 is added. The isocyanate content of the prepolymerwas 7.94% (theoretical 8.16%). 29.2 g of triethylamine was added to theprepolymer to neutralise the acid groups and the mixture was homogenisedwith stirring.

A 2000 cm3 dispersion vessel with a thermometer and overhead stirrer wascharged with 994.7 g of demineralised water, 4.7 g of Tegofoamex 805(obtained from Tego), 36.9 g of DSX 1514 (obtained from BASF), 15.3 gDisponil AFX3070 (obtained from BASF) and 46.2 g of MMA. The mixture washomogenised with stirring and the temperature was adjusted to 20-22° C.

421.9 g of the neutralised prepolymer was dispersed in the aqueous phaseadjusting the stir rate to improve dispersing of the prepolymer ifnecessary, while maintaining the temperature of the aqueous phase below27° C. After the give amount of prepolymer was dispersed, stirring wascontinued for 5 minutes after which a mixture of 26.3 g DETA and 26.3 gof water was added to provide the chain extended polyurethanedispersion.

After 15 minutes of mixing, the radical polymerization was initiated bythe addition of 0.32 g of tertiary butyl hydroperoxide, 0.0035 g ofiron(II)EDTA and a subsequent addition of 21.4 g of a 1.0% solution ofisoascorbic acid in demineralized water.

The resulting polyurethane dispersion had a solids content of 32.7 wt %,a pH of 8.0 and a viscosity of 1046 cps. The dispersion has a D(0.5)mean particle size of 2.2 micron and a D(0.9) mean particle size of 4.9micron.

TABLE 3 Appearance EtOH of coating on Anti- Water resistance Gloss ablack Soft Delta L blocking resistance (after Detergent 60° substratefeel value* (L/L) (direct) recovery) (direct) Comp D 1.6 Matt, whitishVery 33 Very Moderate Poor Moderate good good 5 0.6 Matt, black Very 14Very Good Moderate Good good good *delta L = (L-value of the coating) −(L-value of the substrate = 6.2); coating is applied at 100 micron wetlayer.

Comparative Example D is again an example of a polyurethane dispersionwith low gloss values and soft feel coatings. A negative attribute forthese dispersion is an opaque or whitish appearance. For someapplications it is important that the coating is transparent and thefilm looks black when casted on a black substrate. This aspect isimproved significantly by modifying the chemical composition of thepolyurethane dispersion into a urethane/vinyl hybrid dispersion.Furthermore, the resistance profile is again improved when Example 5 iscompared to Comparative Example D.

TABLE 4 Comp Comp Comp Comp Ex A Ex B Ex C Ex 1 Ex 2 Ex 3 Ex 4 Ex D Ex 5Polyurethane-vinyl No No Yes Yes Yes Yes Yes No Yes polymer hybridparticles Crosslinked Yes No No Yes Yes No Yes Yes Yes polyurethane PUcomponent percentages (relative to total amount of components (a)-(g))(a) 19.9 32.1 32.6 19.9 19.9 32.1 31.7 29.0 29.0 (b) 1.7 2.2 4.9 1.7 1.72.2 2.2 1.6 1.6 (c) 65.9 59.1 61.0 65.9 65.9 59.1 58.3 53.4 53.4 (d) 2.06.5 1.5 2.0 2.0 6.5 2.2 6.0 6.0 (e) 0 0 0 0 0 0 0 0 0 (f) 10.5 0 0 10.510.5 0 5.5 10.1 10.1 (g) 0 0 0 0 0 0 0 0 0 (d′) 0 0 0 0 0 0 0 6.0 6.0Sum of (f), (g) and (d′) 10.5 0 0 10.5 10.5 0 5.5 16.1 16.1 U/A ration/a n/a 4.0 3.8 9.1 2.6 3.9 n/a 9.5

The invention claimed is:
 1. An aqueous coating composition comprisingdispersed polymer particles, wherein (i) the dispersed polymer particlesare polyurethane-vinyl polymer hybrid particles obtained by free-radicalpolymerization of at least one vinyl monomer in the presence of apolyurethane, (ii) the polyurethane and the vinyl polymer in the hybridparticles are present in a weight ratio of polyurethane to vinyl polymerranging from 3:1 to 10:1, (iii) the polyurethane is obtained by thereaction of at least the following components: (a) from 10 to 35 wt. %of at least one organic difunctional isocyanate, (b) from 1 to 2.5 wt %of an isocyanate-reactive compound containing ionic or potentially ionicwater-dispersing groups having a molecular weight of from 100 to 500g/mol, (c) from 50 to 70 wt. % of at least one diol having a molecularweight from 500 to 5000, (d) from 0.5 to 10 wt. % of at least oneactive-hydrogen chain extending compound with a functionality of atleast 2 other than water, (e) from 0 to 10 wt. % of at least one diolhaving a molecular weight below 500 g/mol, wherein the amounts of (a),(b), (c), (d) and (e) are given relative to the total amount ofcomponents used to prepare the polyurethane from which the buildingblocks from the polyurethane are emanated, and wherein the isocyanate(NCO) groups and hydroxy (OH) groups on the components used to preparethe polyurethane are present in a respective mole ratio of NCO groups toOH groups in a range of from 1.05:1 to 5:1, (iv) the dispersed polymerparticles have a mean particle size (D[0.5]) greater than 1.2 micron,(v) the dispersed polymer particles have a mean particle size (D[0.9])less than 6 micron, and (vi) the polyurethane of the polyurethane-vinylpolymer hybrid particles is crosslinked.
 2. The aqueous coatingcomposition according to claim 1, wherein the coating compositioncomprises (A) 75 to 99.7 wt. % of the dispersed polymer particles, (B)0.2 to 15 wt. % of a rheology additive, and (C) 0.1 to 10 wt. % of asurfactant, wherein the amounts of (A), (B) and (C) are given relativeto the total amount of (A), (B) and (C).
 3. The aqueous coatingcomposition according to claim 1, wherein at least 30 wt. % of the totalamount of the at least one vinyl monomer used to prepare the vinylpolymer is selected from the group consisting of methyl methacrylate,butyl acrylate, butyl methacrylate, acrylonitrile, styrene and mixturesof two or more of said monomers.
 4. The aqueous coating compositionaccording to claim 1, wherein the diol (c) has a glass transitiontemperature Tg from −110° C. to +110° C.
 5. The aqueous coatingcomposition according to claim 1, wherein the crosslinked polyurethaneis prepared by further adding at least one of the following crosslinkercomponents (f), (g) and (d′): (f) from 1 to 20 wt. % of at least oneorganic polyisocyanate with an average functionality of >2.3; (g) from 1to 10 wt. % of at least one polyol having a molecular weight of 500-5000g/mol, an average functionality of at least 2.3, and a glass transitiontemperature Tg from −110° C. to +110° C.; and (d′) at least oneactive-hydrogen chain extending compound with a functionality of 3 orhigher in an amount of at least 50 wt. % of the component (d), whereinthe amounts of the components (f), (g) and (d′) are given relative tothe total amount of components (a), (b), (c), (d), including d′), (e),(f) and (g), used to prepare the polyurethane.
 6. The aqueous coatingcomposition according to claim 5, wherein the total amount of thecomponents (f), (g) and (d′) are together more than 3 wt. %, relative tothe total amount of components (a), (b), (c), (d), (d′), (e), (f) and(g) used to prepare the polyurethane, and wherein the total amount ofthe components (f), (g) and (d′) are together at most 20 wt. %, relativeto the total amount of the components (a), (b), (c), (d), (d′), (e), (f)and (g) used to prepare the polyurethane.
 7. The aqueous coatingcomposition according to claim 5, wherein the component (d′) is apolyamine with a functionality of
 3. 8. The aqueous compositionaccording to claim 5, wherein the component (f) is selected from thegroup consisting of hexamethylene diisocyanate isocyanurate,hexamethylene diisocyanate biuret, isophorone diisocyanate isocyanurateand mixtures thereof.
 9. The aqueous coating composition according toclaim 1, wherein the dispersed polymer particles (A) have a meanparticle size (D[0.5]) which is greater than 1.5 micron.
 10. The aqueouscoating composition according to claim 1, wherein the total amount ofactive-hydrogen chain extending compound employed, if used, apart fromwater, is such that the molar ratio of active hydrogens in the chainextender to isocyanate groups in the polyurethane prepolymer is in arange from 0.1:1 to 2:1.
 11. The aqueous coating composition accordingto claim 1, wherein the aqueous coating composition is free of organicsolvent.